The present invention relates to a contact device for a keyswitch used in an electronic instrument such as portable telephone, and more particularly relates to a contact device in a key sheet module used in a keyswitch operated by a key top.
FIG. 10 is a plan view showing a conventional key sheet module, FIG. 11 is an enlarged sectional view taken along a line XIxe2x80x94XI of FIG. 10, and FIG. 12 is a plan view of fixed contacts.
The key sheet module 81 comprises a substrate 82, and a plurality of keyswitches 83 provided on the substrate 82.
Referring to FIGS. 11 and 12, the keyswitch 83 comprises a first circular fixed contact 86 secured on the substrate 82, and a second annular fixed contact 87 provided around the first fixed contact 86, and a movable contact 85 having a semispherical shape and mounted on the second fixed contact 87. The first fixed contact 86 is connected to a circuit pattern 88 provided on the underside of the substrate 82 by a connecting pipe 82a secured to a wall of a through-hole formed in the substrate 82. The second fixed contact 87 is connected to a circuit pattern 89 provided on the upper surface of the substrate 82. An adhesive sheet 84 is adhered to the substrate 82 to hold the movable contact 85 each of the keyswitches 83.
When the movable contact 85 is pressed by a key (not shown), the contact 85 contacts with the first fixed contact 86. Thus, the first and second fixed contacts 86 and 87 are connected with each other.
In the conventional keyswitch, since circuit patterns 88 and 89 are provided on both surfaces of the substrate 82, the manufacturing cost increases. Further, there are two different manufacturing steps comprising the soldering on the circuit patterns 88 and 89 and the adhering of the adhesive sheet 84, which increases further the manufacturing cost.
An object of the present invention is to provide a contact device which may be manufactured at a low cost.
According to the present invention, there is provided a keyswitch comprising a circuit substrate, a first fixed contact mounted on an upper surface of the circuit substrate, a second fixed contact mounted on the upper surface of the circuit substrate around the first fixed contact, a movable contact having a semicircular sectional shape and mounted on the second fixed contact, terminal electrodes provided on an underside of the circuit substrate and connected to the first and second fixed contacts respectively, a spacer mounted on the circuit substrate so as to surround the movable contact, and a cover mounted on the spacer to cover the movable contact.
The movable contact has a plurality of feet so as to hold the movable contact, and the second fixed contact has an opening. The first fixed contact is connected to the terminal electrode by a conductive pattern formed on the circuit substrate in the opening.